Drive device for PTO shaft of working machine

ABSTRACT

A drive device for a PTO shaft includes a parking switch to detect a parking state of a vehicle body, a permission switch constituted of a self-returning switch and connected to the parking switch, the permission switch being configured to be switched to permit driving a PTO shaft, the PTO shaft being configured to be driven by a power of a prime mover disposed on the vehicle body, and a first switch device to be switched to enable the PTO shaft to be driven when the permission switch is switched to permit driving the PTO shaft under a state where the parking switch detects the parking state of the vehicle body.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. applicationSer. No. 15/627,741, filed Jun. 20, 2017, which claims priority under 35U.S.C. § 119 to Japanese Patent Application No. 2016-123937, filed Jun.22, 2016 and to Japanese Patent Application No. 2016-123938, filed Jun.22, 2016. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a drive device for a PTO shaft of a wokmachine.

Discussion of the Background

Japanese patent application publication No. 2012-30616 and Japanesepatent application publication No. 2013-132936 disclose the techniquesrelating to a driving method of a PTO shaft of a work machine such as atractor, the PTO shaft being configured to be driven by an engine.

The tractor disclosed in Japanese patent application publication No.2012-30616 includes a PTO select switch, a detection switch, and acontrol device. The PTO select switch is configured to turn on and offthe driving of the PTO shaft. The detection switch is configured todetect a state of a parking brake. The control device is configured tocontrol the stopping of the engine, that is, the driving of the PTOshaft on the basis of the states of the PTO select switch and thedetection switch. In the case where the PTO select switch is tuned onand the detection switch detects the activation of the parking brake,the control device maintains the driving of the PTO shaft withoutstopping the engine.

The tractor disclosed in Japanese patent application publication No.2013-132936 includes an internal PTO switch and an external PTO switch.The internal PTO switch is arranged inside a cabin of the tractor andthe like and configured to turn on and off the driving of the PTO shaft.The external PTO switch is arranged on a fender of the tractor and isconfigured to turn on and off the driving of the PTO shaft. When adriver (an operator) in the cabin operates the internal PTO switch, thePTO shaft is to be driven. In addition, when an operator outside thecabin operates the external PTO switch, the PTO shaft is to be driven.

SUMMARY OF THE INVENTION

A drive device for a PTO shaft of a work machine includes a parkingswitch to detect a parking state of a vehicle body, a permission switchconstituted of a self-returning switch and connected to the parkingswitch, the permission switch being configured to be switched to permitdriving a PTO shaft, the PTO shaft being configured to be driven by apower of a prime mover disposed on the vehicle body, and a first switchdevice to be switched to enable the PTO shaft to be driven when thepermission switch is switched to permit driving the PTO shaft under astate where the parking switch detects the parking state of the vehiclebody.

A drive device for a PTO shaft of a work machine includes a parkingswitch to detect a parking state of a vehicle body, a first switcharranged on an operation portion disposed on the vehicle body, the firstswitch being configured to be switched to enable the PTO shaft to bedriven, the PTO shaft being disposed on the vehicle body, a secondswitch arranged on a portion different from the operation portion, thesecond switch being configured to be switched to enable the PTO shaft tobe driven; and a controller to drive the PTO shaft when any one of thefirst switch and the second switch is turned on, wherein the controllerincludes a first controller to stop driving the PTO shaft when theparking switch does not detect the parking state of the vehicle bodyunder a state where the second switch is turned on to drive the PTOshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view illustrating a general configuration of aspeed-change device according to a first embodiment of the presentinvention;

FIG. 2 is a general view illustrating a drive device for a PTO shaftaccording to the first embodiment;

FIG. 3 is a general view illustrating a drive device for a PTO shaftaccording to a second embodiment of the present invention;

FIG. 4 is a general view illustrating a drive device for a PTO shaftaccording to a third embodiment of the present invention;

FIG. 5 is a view illustrating a part of a speed-change device accordingto the third embodiment;

FIG. 6 is a view illustrating an alarm mechanism of a drive device for aPTO shaft according to a fourth embodiment of the present invention;

FIG. 7 is a view illustrating a flowchart of operations of a controldevice and an alarm device according to the fourth embodiment;

FIG. 8 is a general view illustrating a drive device for a PTO shaftaccording to a fifth embodiment of the first embodiment;

FIG. 9A is a view illustrating a motion of a first switch (an internalPTO switch) from the side according to the fifth embodiment;

FIG. 9B is a plan view illustrating the first switch (the internal PTOswitch) according to the fifth embodiment;

FIG. 10 is a view illustrating processes of a PTO control and anengine-starting check in blocks according to the fifth embodiment;

FIG. 11 is a view illustrating a phase transition relating to the PTOcontrol and the engine-starting check according to the fifth embodiment;

FIG. 12 is a view illustrating an inside of a cabin according to theembodiments; and

FIG. 13 is a general view illustrating a work machine according to theembodiments.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings. The drawings are tobe viewed in an orientation in which the reference numerals are viewedcorrectly.

Referring to drawings, an embodiment of the present invention will bedescribed below.

First Embodiment

FIG. 13 illustrates a general view of a work machine a according to afirst embodiment of the present invention, the work machine 1 having adrive device for a PTO shaft. The work machine 1 illustrated in FIG. 13is a tractor. However, the work machine 1 is not limited to the tractor,and may be an agricultural machine such as a combine and a rice plantingmachine, a construction machine, and the like.

A general configuration of the tractor 1 will be explained first.

As shown in FIG. 13, the tractor 1 includes a traveling vehicle body(hereinafter referred to as a vehicle body) 3, a prime mover 4, and aspeed-change device 5. The vehicle body 3 includes wheels. The primemover 4 is constituted of any one of a diesel engine, a gasoline engine,an electric motor, and the like. In the embodiment, the prime mover 4 isconstituted of the diesel engine (hereinafter simply referred to as anengine).

The vehicle body 3 is provided with an operator seat 6 and a cabin 7surrounding the operator seat 6. In addition, a connection portion (aconnector) 8 is disposed on a rear portion of the vehicle body 3. Theconnection portion 8 is constituted of a three-point linkage mechanismor the like. A work device 2 is configured to be attached to anddetached from the connection portion 8. For example, the work device 2such as a tilling device (a tiller), a fertilizing device (afertilizer), a chemicals distribution device (a chemicals distributor),or the like is connected to the connection portion 8, and thereby thetravel vehicle body 3 trails the work device 2.

As shown in FIG. 1, the speed-change device 5 includes a main shaft (athrust shaft) 5 a, a main speed-change portion (a main speed changer) 5b, a sub speed-change portion (a sub speed changer) 5 c, a shuttleportion (a shuttle) 5 d, and a PTO power transmitting portion (a PTOpower transmission) 5 e. The thrust shaft 5 a is supported rotatably bya housing case of the speed-change device 5, and thereby a motive poweroutputted from a crank shaft of the engine 4 is transmitted to thethrust shaft 5 a.

The main speed-change portion 5 b includes a plurality of gears and ashifter. The shifter is configured to change the linkage (engagement)between the plurality of gears. The main speed-change portion 5 barbitrarily changes the linkage (engagement) between the plurality ofgears with use of the shifter, thereby changing and outputting therevolution inputted from the thrust shaft 5 a (changing the speed).

The sub speed-change portion 5 c includes a plurality of gears and ashifter as in the main speed-change portion Sc. The shifter isconfigured to change the linkage (engagement) between the plurality ofgears. The sub speed-change portion 5 c arbitrarily changes the linkage(engagement) between the plurality of gears with use of the shifter,thereby changing and outputting the revolution inputted from the mainspeed-change portion 5 b (changing the speed).

The shuttle portion 5 d includes a shuttle shat 12 and aforward-movement backward-movement switch portion (a forward-movementbackward-movement switch) 13. A motive power outputted from the subspeed-change portion 5 c is transmitted to the shuttle shaft 12 throughthe gears. The forward-movement backward-movement switch portion 13 isconstituted of a hydraulic clutch or the like, for example. Theforward-movement backward-movement switch portion 13 engages thehydraulic clutch and releases the engagement, thereby switching arevolution direction of the shuttle shaft 12, that is, one of theforward movement and the backward movement of the tractor 1 to theother.

The PTO power transmitting portion 5 e includes a PTO thrust shaft 14and a PTO clutch 15. The PTO thrust shaft 14 is supported rotatably, andis capable of transmitting a motive power outputted from the thrustshaft 5 a. The PTO thrust shaft 14 is connected to the PTO shaft 16 bythe gears or the like.

The PTO clutch 15 is constituted of a clutch configured to be switchedfrom any one of a first movement and a second movement to the other. Thefirst movement transmits the motive power of the thrust shaft 5 a to thePTO thrust shaft 14. The second movement does not transmit the motivepower of the thrust shaft 5 a to the PTO thrust shaft 14.

In particular, the PTO clutch 15 is constituted of a hydraulic clutch,and includes a housing 15 a, a clutch member 15 b, and a piston 15 c.The housing 15 a is configured to turn integrally with the PTO thrustshaft 14. The clutch member 15 b is configured to turn integrally withthe thrust shaft 5 a. The piston 15 c is configured to move in thehousing 15 a with use of the operation fluid.

In this manner, when the piston 15 c is moved to make the clutch member15 b contact to the housing 15 a, the PTO clutch 15 shifts to the firstmovement, the motive power from the engine 4 is transmitted to the PTOthrust shaft 14 through the thrust shaft 5 a and the PTO clutch 15, andthen a motive power of the PTO thrust shaft 14 is transmitted to the PTOshaft 16.

That is, the PTO shaft 16 is driven by the motive power of the engine 4through the speed-change device 5. On the other hand, when the piston 15c is moved to the opposite direction to make the clutch member 15 bseparate from the housing 15 a, the PTO clutch 15 shifts to the secondmovement, the motive power from the thrust shaft 5 a is not transmittedto the PTO thrust shaft 14, and then a motive power of the PTO thrustshaft 14 is cut off.

Meanwhile, the transmitting and the cutting-off of the motive power bythe PTO clutch 15 are carried out by an operation valve 17 (a switchvalve) connected to the piston 15 c by a fluid tube (a fluid path). Apump 18 is connected to the operation valve 17. The pump 18 isconfigured to supply the operation fluid (a fluid).

FIG. 2 illustrates a drive device 20 for the PTO shaft.

The drive device 20 for the PTO shaft includes a parking switch (aparking SW) 21, a permission switch (a permission SW) 22, an on-offswitch (an on-off SW) 23, a first switch device 24, and a second switchdevice 25. The drive device 20 for the PTO shaft includes a seat switch26.

The parking switch 21 is constituted of a switch configured to detectthe parking of the travel vehicle body (the vehicle body) 3. Inparticular, the parking switch 21 is configured to be switched to be ONand to be OFF. The parking switch 21 is switched to be ON by theswinging of the parking lever when a parking lever (a parking brake) ispositioned at a position (a brake position) to brake the vehicle body 3,and thereby the parking is detected.

The parking switch 21 is switched to be OFF by the swinging of theparking lever when the parking lever is positioned at a position (arelease position) to release the braking of the vehicle body 3, andthereby the parking is not detected.

The permission switch 22 is constituted of a switch configured to beswitched to permit or not to permit driving the PTO shaft 16. Thepermission switch 22 is a switch to be operated by an operator (adriver), and is arranged in the vicinity of the operator seat, on a sideportion of the vehicle body 3, or on a rear portion of the vehicle body3, for example.

Meanwhile, an arrangement position of the permission switch 22 is notlimited to the positions mentioned above. For convenience of theexplanation, the permission relating to the driving of the PTO shaft 16will be referred to as “a PTO permission” below, and the non-permissionrelating to the driving of the PTO shaft 16 will be referred to as “aPTO non-permission” below.

The permission switch 22 is configured to be switched to be ON and to beOFF, and is constituted of a self-returning switch. The self-returningswitch does not maintain an ON state and an OFF state after theswitching. For example, the permission switch 22 is constituted of amomentary switch. The permission switch 22 provides the PTO permissionunder the ON state and provides the PTO non-permission under the OFFstate.

The on-off switch 23 is configured to switch the driving of the PTOshaft 16 to be turned on and to be turned off. For example, the on-offswitch 23 sets the driving of the PTO shaft 16 to be turned on under theON state and to be turned off under the OFF state.

The on-off switch 23 is arranged in the vicinity of the operator seat 6,and is configured to be operated by the operator (the driver). When theon-off switch 23 is switched to be ON, the operation valve 17 isswitched to a predetermined position, the PTO clutch 15 performs thefirst movement, and thereby the PTO shaft 16 is driven (revolved).

On the other hand, when the on-off switch 23 is switched to be OFF, theoperation valve 17 is switched to another predetermined position, thePTO clutch 15 performs the second movement, and thereby the PTO shaft 16stops being driven (revolved).

The seat switch 26 is constituted of a switch configured to detect theoperator seated on the operator seat 6 (that is, to detect the seatingon the operator seat 6). For example, the seat switch 26 is configuredto be switched to be ON and to be OFF. The seat switch 26 is arranged ina seat of the operator seat 6 (a bottom seat, a backrest), under theseat, or the like.

When the operator is seated on the seat, the seat switch 26 is switchedto be ON, and thereby detecting the seating. In addition, when theoperator gets off the seat, the seat switch 26 is switched to be OFF,and thereby not detecting the seating (detecting the not-seating(absence)).

The first switch device 24 is constituted of a device configured to beswitched to enable the PTO shaft to be driven when the permission switch22 is switched to permit driving the PTO shaft (switched to be ON) undera state where the parking switch 21 detects the parking state of thevehicle body 3. The first switch device 24 is constituted of any one ofa dynamic relay (a contact relay), a static relay (a contactless relay),a sequencer, and the like.

In the embodiment, the first switch device 24 is constituted of thecontact relay including a coil portion 24 a, a switch portion 24 b, afirst input terminal 24 c, and a second input terminal 24 d.

Meanwhile, the first switch device (the relay) 24 may be “a singlestable type”, “a latching type”, and other types of relays. The singlestable type switches the switch portion 24 b to be ON when the coilportion 24 a is magnetized. The latching type switches the switchportion 24 b by latching the magnetization of the coil portion 24.

The first switch device 24 supplies an electric power to the secondswitch device 25 when an electric current is supplied to the coilportion 24 a to switch the switch portion 24 b to be ON, and thereby thePTO shaft 16 is driven. On the other hand, the first switch device 24stops supplying the electric power to the second switch device 25 whenthe electric current is not supplied to the coil portion 24 a to switchthe switch portion 24 b to be OFF, and thereby the driving of the PTOshaft 16 is stopped.

The second switch device 25 is constituted of a device configured tomaintain and stop the driving of the PTO shaft 16. That is, the secondswitch device 25 includes a third input terminal 25 a, a fourth inputterminal 25 b, and a solenoid (not shown in the drawings). When anelectric current is supplied to the third input terminal 25 a and thefourth input terminal 25 b of the second switch device 25, the solenoidis not activated, an operation of the engine 4 is maintained, andthereby the driving of the PTO shaft 16 is maintained.

On the other hand, when the electric supply to the third input terminal25 a of the second switch device 25 is stopped, the solenoid isactivated, a key switch (an ignition switch) 28 is switched to be off(to an engine stopping position). In this manner, the driving of the PTOshaft 16 is stopped. In the embodiment, the second switch device 25turns on and off the operation of the engine 4, and thereby stopping thedriving of the PTO shaft 16. However, the second switch device 25 mayemploy another method.

In addition, the second switch device 25 may include a timer. That is,the timer counts a duration time (a releasing time) of the releasing ofthe electric supply to the third input terminal 25 a of the secondswitch device 25. In this manner, the solenoid may be activated when thereleasing time reaches a predetermined time, and thus the key switch 28may be switched to be off (to the engine stopping position).

Connections between the parking switch 21, the permission switch 22, theon-off switch 23, the first switch device 24, the second switch device25, and the seat switch 26 will be explained next.

An input terminal 21 a of the parking switch 21 is connected to anelectric power source system. An output terminal 21 b of the parkingswitch 21 is connected to an input terminal 22 a of the permissionswitch 22. That is, the parking switch 21 and the permission switch 22are connected in series to each other.

An output terminal 22 b of the permission switch 22 is connected to afirst input terminal 24 c of the first switch device 24. That is, anoutput terminal 22 b of the permission switch 22 is connected to thecoil 24 a of the first switch device 24.

An input terminal 23 a of the on-off switch 23 is connected to theelectric power source system. An output terminal 23 b of the on-offswitch 23 is connected to a second input terminal 24 d of the firstswitch device 24. That is, an output terminal 23 b of the on-off switch23 is connected to one end of the switch 24 b.

Thus, in view of the first switch device 24, the permission switch 22 isconnected to the first input terminal 24 c of the first switch device24. The on-off switch 23 is connected to the second input terminal 24 dof the first switch device 24. Meanwhile, the permission switch 22 andthe on-off switch 23 may be connected to the first switch device 24inversely.

That is, the output terminal 22 b of the permission switch 22 may beconnected to the second input terminal 24 d of the first switch device24. The output terminal 23 b of the on-off switch 23 may be connected tothe first input terminal 24 c of the first switch device 24.

The output terminal 24 e of the first switch device 24 is connected tothe third input terminal 25 a of the second switch device 25. Inaddition, the output terminal 26 b of the seat switch 26 is connected tothe third input terminal 25 a of the second switch device 25.

Meanwhile, the input terminal 26 a of the seat switch 26 is connected tothe electric power source. The fourth input terminal 25 b of the secondswitch device 25 is connected to the electric power source.

As shown in FIG. 2, in view of the connections between the switches (theparking switch 21, the permission switch 22, the on-off switch 23, andthe seat switch 26) and the switch devices (the first switch device 24and the second switch device 25), the drive device 20 for the PTO shaftincludes a first system L1, a second system L2, and a third system L3.

Each of the first system L1, the second system L2, and the third systemL3 is constituted of the wiring members and the like connecting theswitches and the switch devices to each other.

The first system L connects the parking switch 21 and the permissionswitch 22 in series to each other, and further connects the outputterminal 22 b of the permission switch 22 to the first input terminal 24c of the first switch device 24.

Meanwhile, reversing the order of the series connection between theparking switch 21 and the permission switch 22 shown in FIG. 1, areversed system connecting the output terminal 22 b of the parkingswitch 21 to the first input terminal 24 c of the first switch device 24may be referred to as the first system L1.

The second system L2 connects the output terminal 22 b of the on-offswitch 23 to the second input terminal 24 of the first switch device 24,and connects the output terminal 24 e of the first switch device 24 tothe third input terminal 25 a of the second switch device 25.

The third system L3 connects the output terminal 26 b of the seat switch26 to the third input terminal 25 a of the second switch device 25.

Thus, the drive device 20 of the PTO shaft includes the first system L1,the second system L2, and the third system L3. In this manner, thecontrols relating to the driving of the PTO shaft 16 are carried out ineach of the first system L1 to the third system L3, the independency ofthe controls is improved, and thereby improving the safety.

The following explanations describe the working (the stationary PTO)carried out by the motive power of the PTO shaft 16 under the conditionthat the tractor is parked (stopped). For convenience of theexplanations, the ignition switch 28 is turned on and the engine 4 is inoperation before the stationary PTO.

In the working under the stationary PTO, the operator turns on theon-off switch 23. The electric power source (an electric power) of thesecond system L2 is then supplied to the switch 24 b of the first switchdevice 24.

In addition, the operator sets the parking lever to the brake positionand switches the parking switch 21 to be ON. Then, the operator switchesthe permission switch 22 to be ON. The electric power source (anelectric power) of the first system L1 is supplied to the coil 24 b ofthe first switch device 24. In this manner, the first switch device 24is switched to be ON, and thereby the electric voltage (an electriccurrent) supplied to the third input terminal 25 a of the second switchdevice 25.

In this manner, the PTO shaft 16 can be driven under the state where thetractor 1 is parked. That is, when the parking of the vehicle body 3 isdetected and the permission switch is switched to be under the PTOpermission, the work device 2 can perform the working under the statewhere the tractor 1 is parked.

In the case where the permission switch 22 employs a self-retainingswitch, the permission switch 22 is not switched to be under the PTOnon-permission unless the permission switch 22 is pushed again. In thatcase, the permission switch 22 is still ON without the pushing in thecase where the parking lever is set to the brake position again or theignition switch 28 is switched to be ON again after the parking lever isset to the brake release position again or the ignition switch 28 isturned to be OFF again, for example.

Thus, in the case where the permission switch 22 is constituted of theself-retaining switch, not only the operator forgets to return thepermission switch 22, but also the permission switch 22 is capable ofbeing switched to be under the PTO permission constantly, and thus thePTO shaft is driven at the unexpected timing because of the operator'smistake or the like.

Meanwhile, the permission switch 22 is constituted of the self-returningswitch in the embodiment. Thus, in the case where the first switchdevice 24 is the single stable type, the PTO permission is set onlyduring the permission switch 22 is pushed. In the case where the PTOpermission is set only during the permission switch 22 is pushed, thetiming to stop the PTO shaft 16 can be easily set in comparison with theself-retaining type, and thereby the operability can be improved in thestationary PTO.

Additionally, in the case where the PTO permission is set only duringthe permission switch 22 is pushed, the PTO shaft is not driven as inthe self-retaining type even when the operator forgets to return thepermission switch 22, and thereby the PTO shaft is prevented from beingdriven because of the forgetting of returning the permission switch 22.

In the case where the first switch device 24 is the latching type, thePTO permission is switched to the PTO non-permission when some movementsor states are carried out after the permission switch 22 is pushed. Forexample, in the case where the ignition switch 28 is turned to be offfrom on again, the PTO non-permission is set without pushing thepermission switch 22 again.

Meanwhile, the first switch device 24 may be configured to switch thestate from the PTO permission to the PTO non-permission when the parkinglever is positioned to the brake release position.

Second Embodiment

FIG. 3 is a view illustrating the drive device 20 for the PTO shaftaccording to a second embodiment of the present invention. The drivedevice for the PTO shaft according to the second embodiment can beemployed as the drive device for the PTO shaft according to the firstembodiment mentioned above. Explanation of configurations similar to theconfigurations of the first embodiment will be omitted.

As shown in FIG. 3, the drive device 20 for the PTO shaft includes aplurality of first neutral switches 30. The plurality of first neutralswitches 30 are constituted of switches configured to detect that aplurality of devices mounted on the vehicle body 3 are at neutralpositions. The plurality of first neutral switches 30 are disposedrespectively corresponding to the plurality of devices.

The plurality of devices serve as devices configured to perform themovements relating to the traveling, for example, as a forward-backwardswitch valve, a speed-change lever, a clutch pedal, and the like. Theforward-backward switch lever is constituted of a lever configured to beswitched (move) to a forward traveling position, a backward travelingposition, and a neutral position. The forward-backward switch lever atthe forward traveling position switches the shuttle portion 5 d to theforward traveling, and the forward-backward switch lever at the backwardtraveling position switches the shuttle portion 5 d to the backwardtraveling.

The speed-change lever is constituted of a lever configured to change aspeed of the main speed-change portion 5 b or the sub speed-changeportion 5 c, and connected to a shifter by a linkage mechanism and thelike. The speed-change lever is capable of being switched to a neutralposition and positions (speed-change positions) corresponding to thespeed-change of the main speed-change portion 5 b or the subspeed-change portion 5 c. The clutch pedal is swingably supported in thevicinity of the operator seat 6, and connects and cuts off a motivepower transmission to a differential device or a drive shaft supportingthe wheels.

For example, the first neutral switch 30 includes a first switch 30 a, asecond switch 30 b, and a third switch 30 c. The first switch 30 a isconfigured to detect the neutral position of the forward-backward switchlever. The second switch 30 b is configured to detect the neutralposition of the speed-change lever. The third switch 30 c is configuredto detect the neutral position of the clutch pedal.

Each of the first switch 30 a, the second switch 30 b, and the thirdswitch 30 c is a switch configured to be switched to be ON and OFF, andare switched to be ON when detecting the neutral position.

The first switch 30 a, the second switch 30 b, and the third switch 30 care connected in series. An input terminal of the first switch 30 a isconnected to the electric power source system. An output terminal of thethird switch 30 c is connected to the input terminal 23 a of the on-offswitch 23.

In this manner, when all of the first switch 30 a, the second switch 30b, and the third switch 30 c detect the neutral positions, an electricpower can be supplied to the input terminal 23 a of the on-off switch23.

Thus, the first switch device 24 switches the driving of the PTO shaftto be turned on when all of the first neutral switches 30 detect theneutral positions under the state where the on-off switch 23 is switchedto be ON and when the permission switch 22 is switched to permit drivingthe PTO shaft 16 under the state where the parking switch 21 detects theparking of the vehicle body 3.

That is, the first switch device 24 is turned ON when the first neutralswitch 30 detects the neutral positions of at least two travel devices.That is, not only the parking switch 21 but the first neutral switch 30configures the condition to certainly stop (park) the vehicle body 3.

In this manner, the PTO shaft 16 is driven and thus the work device 2performs the working under the state where the tractor 1 steadily parks.

In the embodiment mentioned above, the plurality of first neutralswitches 30 are switches configured to detect the neutral positions ofthree devices. However, the plurality of first neutral switches 30 maybe switches configured to detect the neutral positions of at least twodevices.

In addition, the first neutral switch 30 may be a switch configured todetect the neutral position of a shuttle pool of the speed-changedevice, a switch configured to detect a state (a neutral position) wherethe acceleration pedal to set the traveling is not pressed under thestate where the prime mover is a hydraulic drive device (an HST), oranother switch.

Third Embodiment

FIG. 4 is a view illustrating the drive device 20 for the PTO shaftaccording to a third embodiment of the present invention. FIG. 5 is aview illustrating a part of the speed-change device 5 according to thethird embodiment. The drive device for the PTO shaft according to thethird embodiment can be employed as the drive device for the PTO shaftaccording to the first embodiment and the second embodiment mentionedabove. Explanation of configurations similar to the configurations ofthe first embodiment and the second embodiment will be omitted.

As shown in FIG. 5, the PTO shafts 16 of the tractor 1 are disposed on afront portion of the tractor 1 and on a rear portion of the tractor 1.The PTO shaft 16 on the rear portion and the PTO shaft 16 on the frontportion can be driven separately. In particular, the PTO thrust shaft 14of the PTO power transmitting portion 5 e includes a first PTO thrustshaft 14 a and a second PTO thrust shaft 14 b. The PTO shaft 16 a on therear portion is connected to the first PTO thrust shaft 14 a. The PTOshaft 16 a on the front portion is connected to the second PTO thrustshaft 14 b.

As shown in FIG. 4, the drive device 20 for the PTO shaft includes aplurality of second neutral switches 31. The plurality of second neutralswitches 31 are switches configured to detect the neutrals of theplurality of the PTO shafts (the first PTO thrust shaft 14 a and thesecond PTO thrust shaft 14 b).

Each of the second neutral switch 31 includes a first PTO detectionswitch 31 a and a second PTO detection switch 31 b. Each of the firstPTO detection switch 31 a and the second PTO detection switch 31 b is aswitch configured to be switched to be ON and OFF, and are switched tobe ON when detecting the neutral position.

The first PTO detection switch 31 a and the second PTO detection switch31 b are connected in series. An output terminal of the second PTOdetection switch 31 b is connected to an output terminal of the thirdswitch 30 c. The output terminal of the third switch 30 c is connectedto the input terminal 23 a of the on-off switch 23.

In this manner, an electric power is continuously supplied when theplurality of second neutral switches 31 detect the neutral position ofthe PTO shaft 16, and thus the second switch device 25 is capable ofcontinuously operating the engine 4.

In addition, as shown in FIG. 4, the output terminal of the second PTOdetection switch 31 b may be connected to the switch device 27, and theoutput terminal 26 b of the seat switch 26 may be connected to theswitch device 27 that is connected to a starter.

In that case, the engine 4 can be started when the ignition switch 28 isON under the state where the first PTO detection switch 31 a and thesecond PTO detection switch 31 b are ON and the seat switch 26 is ON.

Fourth Embodiment

FIG. 6 is a view illustrating an alarm mechanism in the drive device 20for the PTO shaft according to a fourth embodiment of the presentinvention. The drive device for the PTO shaft according to the fourthembodiment can be employed as the drive device for the PTO shaftaccording to the first embodiment to the third embodiment mentionedabove.

A circuit configuration of the drive device for the PTO shaft accordingto the fourth embodiment is similar to any one of the circuitconfigurations according to the first embodiment to the thirdembodiment. Explanation of configurations similar to the configurationsof the first embodiment to the third embodiment will be omitted.

As shown in FIG. 6, the drive device 20 for the PTO shaft includes acontrol device (a controller) 33 and an alarm device (an alarm) 34. Thecontrol device 33 is constituted of a CPU or the like, and controls thealarm device 34. The parking switch 21, the permission switch 22, theseat switch 26, and the alarm device 34 are connected to the controldevice 33.

The alarm device 34 is constituted of a speaker, a LED, a liquid crystalpanel, and the like. The alarm device 34 issues an alarm on the basis ofsignals inputted from the parking switch 21, the permission switch 22,and the seat switch 26 to the control device 33. The alarm device 34 isarranged in the vicinity of the operator seat 6 or around the vehiclebody 3.

FIG. 7 is a view illustrating a flowchart of operations of the controldevice 33 and the alarm device 34. At the start in FIG. 7, the ignitionswitch (the key switch) 28 is ON, and the engine 4 is in operation.

As shown in FIG. 7, the control device 33 judges whether the operator isseated on the operator seat 6 under the state where the engine 4 is inoperation (S1).

The control device 33 does not make the alarm device 34 issue an alarm(S2) when the seat switch 26 is ON, that is, the operator is seated onthe operator seat 6 (S1, Yes).

The control device 33 judges whether the vehicle body 3 is in theparking state (S3) when the seat switch 26 is OFF, that is, the operatoris not seated on the operator seat 6 (S1, No).

The control device 33 does not make the alarm device 34 issue the alarm(S2) when the parking switch 21 is ON (S3, Yes), that is, the parkinglever is positioned at the brake position.

The control device 33 makes the alarm device 34 issue the alarm (S4)when the parking switch 21 is OFF (S3, No), that is, the parking leveris positioned at the brake release position.

That is, the alarm device 34 issues an alarm when the seat switch 26does not detect the seating under the state where the parking switch 21does not detect the parking of the vehicle body 3. That is, the alarmdevice 34 issues an alarm when the operator is not seated on theoperator seat 6 and moves away from the tractor 1 under the state thetractor 1 is not parked, and thereby calling attention to the operator.

Fifth Embodiment

FIG. 8 is a general view illustrating the drive device 20 for the PTOshaft according to a fifth embodiment of the present invention.Configurations different from the configurations of the embodimentsmentioned above will be explained below. The general configurations ofthe tractor 1 (the work machine 1) is similar to the configurations ofthe embodiments mentioned above, and thus explanations of the generalconfigurations will be omitted.

As shown in FIG. 13, an operation portion 10 is disposed inside thecabin 7, the operation portion 10 being configured to perform variousoperations of the tractor 1 (the vehicle body 3). The operation portion10 is arranged in front of the operator seat 6, on the side of theoperator seat 6, or the like. The operation portion 10 includes anoperation base 10 a, an operation tool 10 b, and a steering wheel 10 c.The operation base 10 a is arranged to the side of the operator seat 6.The operation tool 10 b is arranged on the operation base 10 a. Thesteering wheel 10 c is arranged in front of the operator seat 6.

The operation tool 10 b is constituted of an operation lever supportedswingably, a switch to be switched, a dial being turnable, or the like.The operation valve 17 is constituted of an electromagnetic valve in theembodiment.

As shown in FIG. 8, the drive device 20 for the PTO shaft includes afirst switch 121, a second switch 122, a parking switch 123, and theswitch device 24. The first switch 121, the second switch 122, and theparking switch 123 are connected to the control device 124. Meanwhile,the switches are indicated by characters “SW” in FIG. 8.

The first switch 121 is disposed on the operation base 10 a of theoperation portion 10, and is a switch to turn on and off the driving ofthe PTO shaft 16. That is, the first switch 121 is a switch capable ofturning on and off the driving of the PTO shaft 16 under the state wherethe operator is seated on the operator seat 6.

In other words, the first switch 121 is a switch used for being operatedunder the state where the operator is boarding on the tractor 1. Thefirst switch 121 meanwhile is one of the operation tools 10 b disposedon the operation base 10 a.

The first switch 121 is capable of being switched to three positions, aneutral position (an N position, a third position) 125 a, an ON position(a first position) 125 b, and an OFF position (a second position) 125 c.When the first switch 121 is at the N position 125 a, a signalrepresenting the N position 125 a is inputted to the control device(controller) 124 through the output terminal 29 a.

In addition, when the first switch 121 is at the ON position 125 b, asignal representing the ON position 125 b is inputted to the controldevice (controller) 124 through an output terminal (a first outputterminal) 129 b. When the first switch 121 is at the OFF position 125 c,a signal representing the OFF position 125 c is inputted to the controldevice (controller) 124 through the output terminal (a second outputterminal) 29 c.

When the first switch 121 is at the N position 125 a, the control device124 recognizes that the first switch 121 is set to the N position. Whenthe first switch 121 is at the ON position 125 b, the control device 124recognizes that the driving of the PTO shaft 16 is set to be turned“on”. When the first switch 121 is at the OFF position 125 c, thecontrol device 124 recognizes that the driving of the PTO shaft 16 isset to be turned “off”.

In the embodiment, the line connecting the control device 124 to theoutput terminal 129 c of the first switch 121 is branched into aplurality of branched lines. In particular, the first switch 121includes the operation portion 121 a. a main body 121 b, and aconnection portion 21 c. The operation portion 121 a is provided for aswitching operation. The main body 121 b includes a plurality of outputterminals (connectors). The connection portion 21 c is disposed on themain body 121 b and connects the lines L11, L12, L13, and L14.

The connection portion 21 c includes a first connection portion 21 c 1,a second connection portion 21 c 2, a third connection portion 21 c 3,and a fourth connection portion 21 c 4. The first connection portion 21c 1 is connected to the output terminal (a connector) 29 a. The secondconnection portion 21 c 2 is connected to the output terminal (aconnector) 129 b. The third connection portion 21 c 3 is connected tothe output terminal (a connector) 129 c. The fourth connection portion21 c 4 is connected to the output terminal (a connector) 129 c at aposition different from the connecting point of the third connectionportion 21 c 3.

The first connection portion 21 c 1 is connected to the first inputportion 132 a of the control device 124 by the first line L11. Thesecond connection portion 21 c 2 is connected to the second inputportion 132 b of the control device 124 by the second line L12.

The third connection portion 21 c 3 is connected to the third inputportion 132 c of the control device 124 by the third line L13. Thefourth connection portion 21 c 4 is connected to the fourth inputportion 132 d of the control device 124 by the fourth line L14.

In this manner, when detecting a signal inputted from at least one ofthe plurality of lines L11, L12, L13, and L14, the control device 124recognizes that the driving of the PTO shaft 16 is set to be turned“off”.

Thus, the driving of the PTO shaft 16 can be stopped with at least oneof the lines L connected to the control device 124 even when the lines Lare broken due to a certain trouble, for example.

As shown in FIG. 9A and FIG. 9B, the first switch 121 is constituted ofa switch configured to be pushed and turned. The operation portion 121 ahas a circular shape in a plan view, and is supported turnably by thesupport portion 121 e.

The main body 121 b is connected to end portion of the support portion121 e. For convenience of the explanation, the operation portion 121 awill be referred to as a turn portion 121 a below.

The N position 125 a corresponds to an upper position at which the turnportion 121 a of the first switch 121 separates from an upper surface 10a 1 of the operation base 10 a. When the turn portion 121 a ispositioned at a lower position close to the upper surface 10 a 1 of theoperation base 10 a by pushing the turn portion 21 from the upperposition (the N position 125 a), the first switch 121 is positioned atthe OFF position 125 c.

In addition, when the turn portion 121 a is turned from the lowerposition (the OFF position) 125 c to a predetermined position, the firstswitch 121 is positioned at the ON position 125 b. When the turn portion121 a is released after the first switch 121 is positioned at thepredetermined position (the ON position 125 b), the turn portion 121 aautomatically returns to the upper position through the lower position.

That is, the first switch 121 is constituted of a momentary switchconfigured to automatically return from the OFF position 125 c to the Nposition 125 a.

The second switch 122 is disposed on a position different from theposition of the operation portion 10, and is constituted of a switchconfigured to turn on and off the driving of the PTO shaft 16. Inparticular, the second switch 122 is constituted of a switch arranged onan upper portion of a rear wheel fender that is disposed outside thecabin 7 or arranged on an rear portion disposed outside the cabin 7.

In particular, the second switch 122 is constituted of a switch disposedin the rear portion or a side portion of the vehicle body 3. In otherwords, the second switch 122 is constituted of a switch to be operatedby the operator got off the tractor 1, which is different from the firstswitch 121.

The second switch 122 is configured to be switched to be ON and OFF,thereby switching the driving of the PTO shaft 16 to be turned on andoff. For example, the driving of the PTO shaft 16 is turned ON when thesecond switch 122 is turned on, and the driving of the PTO shaft 16 isturned off when the second switch 122 is turned OFF.

For convenience of the explanation, the first switch 121 is referred toas “an internal PTO switch 121”, and the second switch 122 is referredto as “an external PTO switch 122”.

The parking switch 123 is constituted of a switch configured to detectthe parking of the travel vehicle body (the vehicle body) 3. As shown inFIG. 8, the parking switch 123 includes a first detection switch 123 aand a second detection switch 123 b.

The first detection switch 123 a is switched to be ON when the parkinglever (the parking brake) is positioned at the position (the brakeposition) braking the vehicle body 3, the parking lever being supportedswingably by the vehicle body 3, and is switched to be OFF when theparking lever is positioned at the position (the release position)releasing the braking of the vehicle body 3.

In addition, the second detection switch 123 b is switched to be ON whenthe brake device is under the braking state, the brake device beingconfigured to brake the vehicle body 3, and is switched to be OFF whenthe brake device is under the state (the brake releasing state) wherethe brake device releases the braking. In particular, the brake deviceis a device configured to lock (stop) the turning of the gears disposedon the drive shaft (for example, the drive shaft transmitting a motivepower to the differential device) included in the speed-change device 5.

The second detection switch 123 b is switched to be ON under the brakingstate where the lock member of the brake device is latched to the gearsof the drive shaft to stop the turning of the drive shaft. In addition,the second detection switch 123 b is switched to be OFF under thebraking state where the lock member of the brake device is separatedfrom the gears of the drive shaft to allow the turning of the driveshaft.

The parking switch 123 detects the parking of the vehicle body 3 whenthe first detection switch 123 a and the second detection switch 123 bare switched to be ON. In addition, the parking switch 123 does notdetect the parking of the vehicle body 3 when the first detection switch123 a and the second detection switch 123 b are switched to be OFF.

The parking switch 123 is constituted of the first detection switch 123a and the second detection switch 123 b in the embodiment. However, theparking switch 123 may be constituted of any one of the first detectionswitch 123 a and the second detection switch 123 b. For example, in thecase where the parking switch 123 is constituted of only the firstdetection switch 123 a, the parking switch 123 detects the parking ofthe vehicle body 3 when the first detection switch 123 a is ON and doesnot detect the parking of the vehicle body 3 when the first detectionswitch 123 a is OFF.

In the case where the parking switch 123 is constituted of only thesecond detection switch 123 b, the parking switch 123 detects theparking of the vehicle body 3 when the second detection switch 123 b isON and does not detect the parking of the vehicle body 3 when the seconddetection switch 123 b is OFF.

In addition, the drive device 20 for the PTO shaft includes a traveldetection device 126, a seat switch 127, and an alarm device 128. Thetravel detection device 126, a seat switch 127, and an alarm device 128are connected to the control device 124.

The travel detection device 126 is constituted of a detection deviceconfigured to detect the traveling (the traveling state) of the vehiclebody 3 (the tractor 1). In particular, the travel detection device 126is a vehicle speed sensor configured to measure a traveling speed of thevehicle body 3 (the tractor 1). The vehicle speed sensor 12 measures thetraveling speed of the vehicle body 3 (the tractor 1) on the basis ofthe revolution speed of the wheels or of the drive shaft for turning thewheels.

That is, the traveling of the vehicle body 3 (the tractor 1) is notdetected when the traveling speed measured by the vehicle speed sensor126 is zero, and the traveling of the vehicle body 3 (the tractor 1) isdetected when the traveling speed measured by the vehicle speed sensor126 is more than zero.

The seat switch 127 is constituted of a switch configured to detect theoperator seated on the operator seat 6. For example, the seat switch 127is configured to be switched to be ON and OFF. The seat switch 127 isarranged in a seat of the operator seat 6 (a bottom seat, a backrest),under the seat, or the like.

When the operator is seated on the seat, the seat switch 127 is switchedto be ON, and thereby detecting the seating. In addition, when theoperator gets off (separates from) the seat, the seat switch 127 isswitched to be OFF, and thereby not detecting the seating (detecting thenot-seating).

The alarm device 128 issues an alarm in accordance with the control ofthe control device 124. The alarm device 128 is constituted of aspeaker, a LED, a liquid crystal panel, and the like. The alarm device128 is arranged on the operation portion 10 or around the vehicle body3.

The control device 124 performs the control relating to the driving ofthe PTO shaft 16 (hereinafter referred to as a PTO control). The controldevice 124 drives the PTO shaft 16 or stops the driving of the PTO underthe PTO control. In particular, the PTO drive portion 30 is connected tothe control device 124, the PTO drive portion 30 being configured todrive the PTO shaft 16 and stop the driving.

The PTO drive portion 30 is a stopping device configured to forciblystop the operations of the operation valve (the electromagnetic valve)17 and/or the engine 4.

In order to stop the driving of the PTO shaft 16, the control device 124demagnetizes the solenoid of the operation valve (the electromagneticvalve) 17, thereby operating the PTO clutch 15 in the second movement,and the control device 124 outputs a control signal to the stoppingdevice to active the stopping device, thereby stopping the operation ofthe engine 4.

In addition, in order to drive the PTO shaft 16, the control device 124magnetizes the solenoid of the operation valve (the electromagneticvalve) 17 under the state where the engine 4 is in operation, therebyoperating the PTO clutch 15 in the first movement. The control device124 issues an alarm relating to the driving of the PTO shaft 16 throughthe alarm device 128 under the PTO control.

Meanwhile, when the parking switch 123 is broken down, the alarm device128 may notify the brake-down of the parking switch 123. For example, inthe case where the first detection switch 123 a is switched to be ON andthe second detection switch 123 b is switched to be ON under the statewhere the parking lever is positioned at the brake position, the controldevice 124 determines that the parking switch 123 is not broken down andthe vehicle body 3 is under the parking state.

On the other hand, in the case where the second detection switch 123 bis switched to be OFF and the first detection switch 123 a is switchedto be ON under the state where the parking lever is positioned at thebrake position, the control device 124 determines that the vehicle body3 is under the parking state but the parking switch 123 is broken down.The control device 124 outputs a breakdown notification signal to thealarm device 128 when the control device 124 determines that the parkingswitch 123 is broken down.

The alarm device 128 notifies the breakdown of the parking switch 123 inresponse to the breakdown notification signal. The alarm device 128continues the alarm relating to the breakdown of the parking switch 123in the case where the ignition switch or the accessory switch isswitched to be ON, and stops the alarm relating to the breakdown of theparking switch 123 in the case where the ignition switch or theaccessory switch is switched to be OFF.

The control device 124 executes the PTO control on the basis of thevehicle speed detected by the travel detection device (the vehicle speedsensor) 26 and the conditions of the above-mentioned various switches(the internal PTO switch 121, the external PTO switch 122, the parkingswitch 123, and the seat switch 127).

The control device 124 includes a first control device (a firstcontroller) 124 a, a second control device (a second controller) 124 b,and a third control device (a third controller) 124 c. The first controldevice 124 a, the second control device 124 b, and the third controldevice 124 c are constituted of the electric-electronic devicesconstituting the control device 124, the computer programs stored in thecontrol device 124, and the like.

In addition, the first control device 124 a, the second control device124 b, and the third control device 124 c each execute the PTO control.

The PTO control executed by the first control device 124 a, the secondcontrol device 124 b, and the third control device 124 c will beexplained in detail below.

The first control device 124 a stops the driving of the PTO shaft 16when the parking switch 123 does not detect the parking of the vehiclebody 3 under the state where the PTO shaft 1 is driven in accordancewith the external PTO switch 122 switched to be ON.

In particular, in the case where the operator moves the parking leverfrom the braking position to the releasing position under the statewhere the external PTO switch 122 is switched to be ON during the engine4 is operated and the PTO shaft 16 is driven during the parking switch123 is switched to be ON (in the case where the parking switch 123 isswitched to be OFF), the first control device 124 a demagnetizes thesolenoid of the operation valve 17 to stop the driving of the PTO shaft16.

The second control device 124 b makes the alarm device 128 output analarm in the case where the vehicle speed sensor 126 detects thetraveling of the vehicle body 3 during the PTO shaft 16 is driven andthe seat switch 127 does not detect the seating of the operator.

In particular, the second control device 124 b outputs a signalgenerating the alarm (hereinafter referred to as an alarm-orderingsignal) to the alarm device 128 in the case where the operator separatesfrom the operator seat 6 to switch the seat switch 127 to be OFF duringthe tractor 1 travels (0<the vehicle speed detected by the vehicle speedsensor 126) from the state where the internal PTO switch 121 is switchedto be ON and the seat switch 127 is switched to be ON. The alarm device128 outputs the alarm in accordance with the signal outputted from thesecond control device 24, thereby calling attention to the operator.

Meanwhile, the second control device 124 b may count an elapsed timeafter the seat switch 127 is switched to be OFF (a time after theoperator separates from the operator seat 6), and may output thealarm-ordering signal to the alarm device 128 when the elapsed time is apredetermined time (for example, 1 second) or more.

The third control device 124 c stops the driving of the PTO shaft 16 inthe case where the vehicle speed sensor 126 does not detect thetraveling of the vehicle body 3 during the PTO shaft 16 is driven andwhere the seat switch 127 does not detect the seating of the operator.

In particular, the third control device 124 c demagnetizes the solenoidof the operation valve 17 to stop the driving of the PTO shaft 16 in thecase where the tractor 1 stops traveling from the state where theinternal PTO switch 121 is ON and the seat switch 127 is ON (0=thevehicle speed detected by the vehicle speed sensor 126) during thetractor 1 travels and where the operator separates from the operatorseat 6 to switch the seat switch 127 to be OFF.

Meanwhile, the control device 124 executes a control to check (forbid)the starting of the engine 4 (hereinafter referred to as anengine-starting check). In particular, a check device 131 is connectedto the control device 124, the check device 131 being configured to setthe starter and the like to be OFF.

In order to execute the engine-starting check, the control device 124makes the check device 131 not turn on the starter regardless of theignition switch switched to be ON even when the operator turns on theignition to try to start the engine 4, and thereby the control device124 holds the starter to be OFF. In this manner, the engine 4 cannot bestarted when the engine-starting check is executed.

For example, in the case where the internal PTO switch 121 is not at theN position 125 a at the starting of the engine 4 or in the case wherethe external PTO switch 122 is ON, the control device 124 executes theengine-starting check, and thereby not permitting starting the engine.

On the other hand, in the case where the internal PTO switch 121 is atthe N position 125 a at the starting of the engine 4 and in the casewhere the external PTO switch 122 is OFF, the control device 124 doesnot execute the engine-starting check, and thereby permitting startingthe engine.

FIG. 10 is a view illustrating processes of the PTO control and theengine-starting check in blocks. In addition, FIG. 11 is a viewillustrating a phase transition relating to the PTO control and theengine-starting check.

Referring to FIG. 10, the process of the PTO control and theengine-starting check will be explained simply first.

As shown in FIG. 10, the process of the PTO control includes a SW alarmprocess A1, a PTO stopping process A2, an first external SW process A3,an second external SW process A4, an internal SW process A5, and anon-seating alarm process A6. The engine-starting check includes a SWconfirmation process B1 and an engine-starting check process B2.

The SW alarm process A1 is a process executed when the internal PTOswitch 121 and the external PTO switch 122 both are switched to be ON.The SW alarm process A1 is a process to output an alarm when theinternal PTO switch 121 and the external PTO switch 122 both areswitched to be ON.

The PTO stopping process A2 is a process to stop the driving of the PTOshaft 16 on the basis of the switch or the state of the traveling.

The first external SW process A3 is a process executed when the externalPTO switch 122 is switched to be ON for a short time. The first externalSW process A3 drives the PTO shaft 16 only for a time during which theexternal PTO switch 122 is ON.

The internal SW process A4 is a process executed when the external PTOswitch 122 is switched to be ON for a long time. The internal SW processA4 holds the driving of the PTO shaft 16 at the timing when the externalPTO switch 122 has been ON for a long time. The internal SW process A5is a process executed when the internal PTO switch 121 is switched to beON. The internal SW process A5 is a process to drive the PTO shaft 16.

The non-seating alarm process A6 is a process executed when the seatswitch is switched to be OFF. The non-seating alarm process A6 is aprocess to output an alarm when a predetermined condition is satisfiedunder the condition that the seat switch 127 is OFF.

The SW confirmation process B1 is a process to confirm the states of theinternal PTO switch 121 and the external PTO switch 122 before thestarting of the engine 4. The engine-starting check process B2 is aprocess to forbids the engine to be started on the basis of theconfirmation results of the internal PTO switch 121 and the external PTOswitch 122 in the SW confirmation process B1.

Referring to FIG. 11, the processes and conditions of theengine-starting check and the PTO control will be explained below.

As shown in FIG. 11, the states of the drive device 20 for the PTO shaftis roughly divided into a waiting state C1, a PTO shaft driving stateC2, a PTO shaft stopping state C3, an alarm state C4, and anengine-starting check state C5.

Under the waiting state C1, the control device 124 waits for the inputbeing ON from the internal PTO switch 121 and the external PTO switch122 (step S11). Under the waiting state C1, the drive device 20 for thePTO shaft shifts from the waiting state C1 to the PTO shaft drivingstate C2 when the internal PTO switch 121 is switched to be ON and theseat switch 127 is switched to be ON (step S12).

Under the PTO shaft driving state C2, the control device 124 outputs asignal representing the driving of the PTO shaft 16 (hereinafterreferred to as a drive signal), that is, a signal to magnetize thesolenoid of the operation valve 17 in the internal SW process A5.

In addition, under the waiting state C1, the drive device 20 for the PTOshaft shifts from the waiting state C1 to the PTO shaft driving state C2when the external PTO switch 122 is switched to be ON and the parkingswitch 123 is switched to be ON (step S13).

Under the PTO shaft driving state C2, in the case where a time duringwhich the external PTO switch 122 is switched to be ON (an elapsed time)is a predetermined time (for example, 3 seconds) or less, that is, ashort time, the control device 124 outputs the drive signal to theoperation valve 17 in the first external SW process A3 during theexternal PTO switch 122 is ON.

In addition, under the PTO shaft driving state C2, the drive device 20for the PTO shaft shifts from the PTO shaft driving state C2 to the PTOshaft stopping state C3 when the external PTO switch 122 is switched tobe OFF from ON (step S14).

Under the PTO shaft stopping state C3, the control device 124 outputs asignal representing the stopping of the driving of the PTO shaft 16(hereinafter referred to as a drive stopping signal), that is, a signalto demagnetize the solenoid of the operation valve 17 in the PTOstopping process A2.

In addition, under the PTO shaft driving state C2, in the case where atime during which the external PTO switch 122 is switched to be ON (anelapsed time) is more than a predetermined time (for example, more than3 seconds), that is, a long time, the control device 124 continuouslyoutputs the drive signal to the operation valve 17 in the secondexternal SW process A4, and thereby maintains the PTO shaft drivingstate C2 (step S15).

Under the PTO shaft driving state C2, in the case where any one of theinternal PTO switch 22 and the external PTO switch 122 is switched to beOFF under the state where the PTO shaft 16 is driven continuously in theinternal SW process A5 or the PTO shaft 16 is driven continuously in thesecond external SW process A4, the drive device 20 for the PTO shaftshifts from the PTO shaft driving state C2 to the PTO shaft stoppingstate C3 (step S16).

The control device 124 outputs the drive stopping signal to theoperation valve 17 in the PTO stopping process A2. In addition, underthe PTO shaft driving state C2, in the case where the parking switch 123is switched to be OFF in the PTO shaft driving state C2 under the statewhere the PTO shaft 16 is continuously driven in the second external SWprocess A4, the drive device 20 for the PTO shaft shifts from the PTOshaft driving state C2 to the PTO shaft stopping state C3 (step S17).

The first control device 124 a of the control device 124 outputs thedrive stopping signal to the operation valve 17 in the PTO stoppingprocess A2.

In addition, under the PTO shaft driving state C2, in the case where thevehicle speed detected by the vehicle speed sensor 126 is zero and atime during which the seat switch 127 is OFF is a predetermined time(for example, 1 second) or more under the state where the PTO shaft 16is continuously driven in the internal SW process A5, the drive device20 for the PTO shaft shifts from the PTO shaft driving state C2 to thePTO shaft stopping state C3 (step S18).

The third control device 124 c of the control device 124 outputs thedrive stopping signal to the operation valve 17 in the PTO stoppingprocess A2.

In addition, under the PTO shaft driving state C2, in the case where thevehicle speed detected by the vehicle speed sensor 126 is more than zeroand a time during which the seat switch 127 is OFF is 1 second or moreunder the state where the PTO shaft 16 is continuously driven in theinternal SW process A5, the drive device 20 for the PTO shaft shiftsfrom the PTO shaft driving state C2 to the alarm state C4 (step S19).

The second control device 124 b of the control device 124 outputs thealarm-ordering signal to the alarm device 128 in the non-seating alarmprocess A6.

Under the alarm state C4, in the case where a time during which the seatswitch 127 is OFF is a predetermined time (for example, 0.5 second) orless, the drive device 20 for the PTO shaft shifts from the alarm stateC4 to the PTO shaft driving state C2 (step S20).

Under the PTO shaft driving state C2, the second control device 124 b ofthe control device 124 outputs an alarm-releasing signal to the alarmdevice 128, and thereby the alarm device 128 stops the alarm.

In addition, under the PTO shaft stopping state C3, the drive device 20for the PTO shaft shifts to the waiting state C1 when the driving of thePTO shaft 16 is stopped (step S21).

Under the waiting state C1 or the PTO shaft driving state C2, in thecase where the internal PTO switch 121 and the external PTO switch 122are both ON, the drive device 20 for the PTO shaft shifts to the alarmstate C4 (step S22).

The control device 124 outputs the alarm-ordering signal to the alarmdevice 128 in the SW alarm process A1. The alarm device 128 notifiesthat both of the internal PTO switch 121 and the external PTO switch 122are ON.

Meanwhile, under the waiting state C1, the control device 124 monitorsthe states of the internal PTO switch 121 and he external PTO switch 122in the SW confirmation process B1 (hereinafter referred to as the switchmonitoring). Under the state where the control device 124 executes theswitch monitoring, the drive device 20 for the PTO shaft shifts from thewaiting state C1 to the engine-starting check state C5 when the internalPTO switch 121 is not positioned at the N position 125 a (S23).

In addition, under the state where the control device 124 executes theswitch monitoring, the drive device 20 for the PTO shaft shifts from thewaiting state C1 to the engine-starting check state C5 when the externalPTO switch 122 is ON (S24).

Under the engine-starting check state C5, the control device 124 makesthe check device 131 hold the starter to be OFF, and thereby the controldevice 124 prevents the engine 4 from being started regardless of theignition switch switched to be ON.

Under the engine-starting check state C5, in the case where the internalPTO switch 121 is positioned at the N position 125 a and the externalPTO switch 122 is OFF, the drive device 20 for the PTO shaft shifts fromthe engine-starting check state C5 to the waiting state C1 (step S25).

That is, under the waiting state C1, the control device 124 permits theengine to be started by the ignition switch turned to be ON.

According to the embodiments mentioned above, the control device 124stops the driving of the PTO shaft in the case where the parking switch123 does not detect the parking of the parking switch 123 under thestate where the PTO shaft 16 is driven in accordance with the externalPTO switch 122.

As described above, the driving of the PTO shaft 16 can be stoppedcertainly in the case where another operator boards on the tractor 1 andthen releases the parking of the tractor 1 or the parking of the tractor1 is released because of other conditions under the state where theoperator turns on the external PTO switch 122 of the tractor 1 parkedalready and the operator operates the working outside the tractor 1. Inthis manner, both of the good operability and the high safety can beprovided.

The control device 124 makes the alarm device 128 output an alarm in thecase where the travel detection device 126 detects the traveling duringthe PTO shaft 16 is driven and the seat switch 127 does not detect theseating of the operator. The control device 124 stops driving the PTOshaft 16 in the case where the travel detection device 126 does notdetect the traveling during the PTO shaft 16 is driven and the seatswitch 127 does not detect the seating of the operator.

In this manner, in the case where the operator is not seated on theoperator seat 6 under the state where the tractor 1 travels operatingthe work device 2, the operator can be prompted to be seated on theoperator seat 6 in the traveling of the tractor 1 and in the operationof the work device 2.

On the other hand, even in the case where the operator is not seated onthe operator seat 6, the driving of the PTO shaft 16 can beautomatically stopped when the travel detection device 126 detects thestopping of the tractor 1. In this manner, both of the good operabilityand the high safety can be provided.

In the internal PTO switch 121, the second output terminal 129 c isconnected to the control device 124 by the plurality of lines L, thesecond output terminal 129 c being configured to transmit the OFF of theinternal PTO switch 121. In this manner, the control device 124 canrecognize the OFF of the internal PTO switch 121 with at least one ofthe lines L11 connected to the control device 124 even when the linesL11 are broken due to a certain trouble, for example.

That is, the configuration capable of driving the PTO shaft 16 inaccordance with the internal PTO switch 121 is capable of stopping thePTO shaft 16 more certainly in accordance with the internal PTO switch121.

The control device 124 permits the prime mover 4 such as the engine tobe operated in the case where the internal PTO switch 121 is switched tothe N position 125 a and the external PTO switch 122 is switched to beOFF. In this manner, the configuration capable of driving the PTO shaft16 in accordance with any one of the internal PTO switch 121 and theexternal PTO switch 122 is capable of certainly preventing the PTO shaft16 from being driven immediately after the engine 4 is started. In thismanner, both of the good operability and the high safety can beprovided.

In the above description, the embodiment of the present invention hasbeen explained. However, all the features of the embodiments disclosedin this application should be considered just as examples, and theembodiments do not restrict the present invention accordingly. A scopeof the present invention is shown not in the above-described embodimentsbut in claims, and is intended to include all modifications within andequivalent to a scope of the claims.

What is claimed is:
 1. A drive device for a PTO shaft comprising: aparking switch to detect a parking state of a vehicle body; a firstswitch arranged on an operation portion disposed on the vehicle body,the first switch being configured to be switched to enable the PTO shaftto be driven, the PTO shaft being disposed on the vehicle body; a secondswitch arranged on a portion different from the operation portion, thesecond switch being configured to be switched to enable the PTO shaft tobe driven; and a controller to drive the PTO shaft when any one of thefirst switch and the second switch is turned on, wherein the controllerincludes a first controller to stop driving the PTO shaft when theparking switch does not detect the parking state of the vehicle bodyunder a state where the second switch is turned on to drive the PTOshaft, and wherein the first switch is configured to be switched to afirst position representing an ON position where the PTO shaft is beingdriven, a second position representing an OFF position where the PTOshaft is being not driven, and a third position representing a neutralposition where the PTO shaft is in neutral, and the controller permitsoperation of a prime mover when the first switch is positioned at thethird position under a state where the second switch is turned off, theprime mover being disposed on the vehicle body.